Lubrication and finishing of yarns and threads, such as cotton and silk, has been practiced since ancient times. Such yarns and threads, derived from natural-occurring plants and animals such as cotton plants and silkworms, often required lubrication or finishing by "oiling" or "sizing" to facilitate spinning and bundling. Lubricants used were typically natural hydrophobic oils, such as mineral oil or coconut oil. Sometimes, molten waxes such as beeswax were employed which, when cooled, formed a solid lubricating finish. Usually, the fibers were "sized" by applying a lubricant and/or adhesive material to yarn or warp threads in a weaving operation to impart cohesion and lubricity. Historically, sizes have been hard coatings, applied neat and at a higher fiber add-on than spin finishes, and were often based on starch, wax, and other oleophilic materials. For example, U.S. Pat. No. 1,681,745 discloses a beeswax-based size for artificial silk (rayon) which is applied molten and solidifies quickly before the thread is wound up, thus assuring bundle cohesion and lubrication in all subsequent operations.
While sizes were useful in facilitating the spinning and bundling of fibers, their presence in finished articles was found to be undesirable. In particular, the oleophilic nature of the sizes was found to adversely effect the soil resistance of the finished article. Sizes also frequently compromised the appearance and handle of the article. Consequently, it became common practice to remove the size from a woven article after its manufacture by scouring the article in hot and/or detergent-containing water. In some instances, these sizes were also removed or reduced to acceptable levels as an inherent part of the dying process, as when the woven article is dyed through immersion in aqueous dye baths. However, this later methodology, in which the scouring and dying steps were effectively combined into a single process, also had its drawbacks. In particular, the presence of sizes in the dye bath frequently had adverse affects on the dying process, while also necessitating frequent replenishment of the dye solution.
After World War II, fibers were introduced which were made from synthetic polymers such as nylon, polyolefin, polyester and acrylic. These new high performance synthetic fibers required the use of special sizes called "spin finishes" during spinning and the subsequent fiber operations (e.g., bundling or sizing) required to produce the final woven article (e.g., fabric or carpet). The spin finish served several functions, including (1) reducing the friction developed as the synthetic fibers passed over metal and ceramic machinery surfaces, (2) imparting fiber-to-fiber lubricity, (3) minimizing electrical static charge buildup (a problem especially pronounced in the manufacture of woven articles from synthetic fibers), and, in some instances, (4) providing cohesion to the fiber. In addition, with proper use of additives, spin finish compositions could be made that were stable to high temperatures and pressures, had a controllable viscosity under application conditions, were non-corrosive, and were relatively safe to both the workers and the environment. (See Pushpa, B. et al., "Spin Finishes," Colourage, Nov. 16-30, 1987 (17-26)). However, as with their sizing predecessors, the spin finishes had to be removed from the articles woven from the fibers, typically by scouring, to minimize soiling problems. See, e.g., U.S. Pat. No. 5,263,308 (Lee et al.), Col. 2, Lines 23-25.
The process of scouring, which is necessitated by the use of sizes and spin finishes, is very undesirable in that it is a tedious process which adds to manufacturing costs, while also posing water pollution problems and health concerns. See, e.g., U.S. Pat. No. 5,263,308 (Lee et al.), Col. 2, Lines 20-24. Accordingly, some attempts have been made to avoid the need for scouring by treating unscoured carpets with agents that improve the soil resistance, handle, and other characteristics of the unscoured carpet to levels acceptable for the intended end use. Thus, U.S. Pat. No. 5,756,181 (Wang et al.) and U.S. Pat. No. 5,738,687 (Kamrath et al.) describe the treatment of unscoured carpet with certain polycarboxylate salts to achieve desirable soil resistance and repellency characteristics. Similarly, U.S. Ser. No. 08/595,592 (Wang et al.) filed Feb. 1, 1996, now U.S. Pat. No. 5,908,663 (Wang et al.), describes the topical treatment of unscoured carpets with various inorganic agents such as silica to improve the soil resistance of the carpet. However, while these treatments work quite well for their intended purpose, they require the incorporation of additional steps and materials, thereby increasing the cost and complexity of the manufacturing process. There is thus a need in the art for a method for making carpets and other woven articles that avoids the need for scouring without necessitating the use of additional treatment steps or agents.
A further problem associated with the use of many conventional spin finishes arises during the manufacturing process itself. The vast majority of spin finishes for synthetic fibers are applied from solution or dispersion in water and/or solvent. Health and safety concerns make high solvent levels in the spin finish impractical unless the solvent is non-toxic, non-flammable, and environmentally neutral. As a practical matter, this has limited the solvent selection to water. Also, aqueous dispersions of spin finishes have been preferred to neat spin finishes because the larger volume of finish applied per fiber weight results in lower application variability. Additionally, the water helps eliminate troublesome static charge, especially when formulated with other additives. (See Postman, W., "Spin Finishes Explained," Textile Research Journal, July 1980 (444-453).
Several examples of aqueous spin finish compositions are known to the art. Thus, U.S. Pat. No. 5,153,046 (Murphy) describes an aqueous finish composition for imparting soil-resistant protection to textile fibers, e.g., nylon yarn, which is stable to the high shear environment of a fiber finish application system. This composition is composed of 1-35% (weight) of nonionic fluorochemical textile anti-soilant, 65-95% of nonionic water-soluble or water-emulsifiable lubricant, and 0.05-15% each of quaternary ammonium or protonated amine surfactant and nonionic surfactant. Preferred lubricants are polyethylene glycol 600 monolaurate and methoxypolyethylene glycol 400 monopelargonate.
U.S. Pat. No. 4,388,372 (Champaneria et al.) describes an improved process for making soil-resistant filaments of a synthetic linear polycarbonamide, preferably 6-nylon and 66-nylon, by applying a water-borne primary spin finish composition comprising a perfluoroalkyl ester, a modified epoxy resin and a non-ionic textile lubricant based on poly(ethylene glycol). Particularly preferred lubricants include n-butyl initiated random copolymers of ethylene/propylene oxide. At Col. 6, Lines 59-61 of the reference, it is noted that "Excessive amounts of textile lubricants in the finish composition can interfere in the durability and effectiveness of the soil-resistant ingredients." Accordingly, much of the lubricant is removed at a later stage of processing when the filaments are subjected to a scouring or dyeing operation (Col. 6, lines 51-55), and application of a secondary fiber finish composition to the spun yarn is recommended at the point between the take up and windup rolls (Col. 12, lines 18-19).
U.S. Pat. No. 4,883,604 (Veitenhansl et al.) describes compositions and methods for smoothing textile fibers and sheet-form textiles made from the fibers. These compositions, which are described as solutions, emulsions, or aqueous dispersions, contain a combination of aliphatic polyether having C.sub.6 -C.sub.24 alkyl radicals and containing 1 to 25 units of polymerized C.sub.2 -C.sub.6 alkylene oxides and oxidized, high-density polyethylene. The concentration of aliphatic polyether in these compositions is from 5% to 30%, with the remainder of the composition being dispersants, softeners, other additives, and water. The compositions are used to improve stitching characteristics of the sheet-formed textiles, and no mention is made of improving soil-resistance or repellency.
U.S. Pat. No. 5,139,873 (Rebouillat) discloses aromatic polyamide fibers which are said to be highly processable and to have high modulus, improved surface frictional properties, scourability, deposition, fibrillation and antistatic properties. The fibers have a coating consisting of (a) 30-70% by weight of a long chain carboxylic acid ester of a long chain branched primary or secondary, saturated, monohydric alcohol, (b) 20 to 50% by weight of an emulsifying system consisting of certain nonionic surfactants, with the remainder being an antistatic agent, a corrosion inhibitor or other optional additives. The scourability of the coating is said to be very important as the residual finish level impacts the subsequent finishing in the case of fabrics (Col. 11, Lines 52-56).
However, the use of low solids aqueous dispersion spin finishes on synthetic fibers has certain disadvantages. Since water possesses a high heat of vaporization, considerable energy is required to evaporate the large quantity of water delivered to the fiber with the spin finish. Furthermore, aqueous dispersions of spin finishes can cause mechanical problems with the fiber line. For example, when conventional low solids aqueous spin finish dispersions are used, the liquid volume of spin finish required during application is fairly large, and this large volume can form non-uniform oily deposits or residues on godets, guides, winders, and other mechanical parts of the fiber-making machinery. These deposits, commonly known as "sling off", either drop to the factory floor or are thrown from the fiber or machinery at various points during the manufacturing process. Sling-off is highly objectionable to fiber manufacturers, due to the cost of clean-up, the damage it can cause to fiber making machinery, and the downtime associated with these problems.
Solid deposition is another major problem which can occur during production, especially when the fiber lubricant is a solid at room temperature and is applied at low solids from an aqueous dispersion. Solid deposition causes a build-up of solids on guides, rolls, and surfaces near the fiber line. The deposition problem is frequently exacerbated by the use of high viscosity spin finishes, the presence of repellent fluorochemicals in the spin finish composition, or the use of spin finish dispersions which go through a gel stage as the water evaporates from the fiber during drying. If the resulting solids are not periodically removed, they will cause fiber breaks. Unfortunately for the fiber manufacturer, the removal of solid depositions is a tedious, expensive and time-consuming process which requires a significant amount of downtime. There is thus a need in the art for spin finish compositions which provide good lubricity and other desirable spin finish characteristics, without exhibiting sling-off or solids deposition during the fiber manufacturing process.
Some attempts have been made to address the problems associated with aqueous spin finish dispersions. In particular, some neat spin finishes have been developed which are solid at room temperature but which can be applied to the fiber in a molten state at elevated temperatures.
U.S. Pat. No. 5,370,804 (Day) describes a neat lubricating finish composition comprising a natural or synthetic ester lubricant and an alkali metal salt of an aliphatic monocarboxylic acid having at least 8 carbon atoms, which melts at temperatures below 150.degree. C. to form a low viscosity liquid to allow uniform coating of the fibers.
U.S. Pat. No. 4,066,558 (Shay et al.) describes a neat, stable yarn lubricating composition having a viscosity of 35-65 centipoise, consisting essentially of a hydrophobic alkyl stearate lubricant, a hydrophilic alcohol ethoxylate or alkylphenol ethoxylate, an antistat and 0.1-5% of a polar coupling agent, such as water, alcohol or glycol ether.
U.S. Pat. No. 3,704,160 (Steinmiller) describes a neat secondary finish comprising oil carrier, metallic fatty acid soap, and tri-fatty acid ester which is a hard waxy material at ambient temperature but, when heated to the molten state (i.e., heated to 50-80.degree. C.), is suitable for treating yarn which is used downstream to make rope having desirable frictional properties for load sharing.
U.S. Pat. No. 4,900,496 (Andrews, Jr. et al.) describes a process for making tire cord made from polyamide yarn by applying a neat hydrophobic organic ester dip penetration regulator having a melting point above 27.degree. C.
U.S. Pat. No. 5,567,400 (Mudge et al.) describes a method for applying a low soil finish to spun synthetic textile fibers containing a dry, waxy solid component solid at room temperature comprising (a) a polyethylenimine bisamide, (b) a block copolymer or ethylene oxide and propylene oxide, (c) the reaction product of a C.sub.8-20 saturated fatty alcohol, a C.sub.8-20 saturated fatty amine, or a phenol with from 2 to 250 moles of ethylene oxide, and/or (d) a C.sub.8-22 fatty acid ester.
Japanese Published Application 6,057,541 describes a neat oil spin finish for synthetic fiber containing lubricant (e.g., butyl stearate or mineral oil), emulsifier and antistatic agent having a viscosity of less than 40 cps at 50.degree. C.
Japanese Published Application 7,252,727 describes a high speed spinning manufacturing process wherein polyamide multifilament is cooled to solidification and a neat oil is applied containing sorbitan ester, polyoxyalkylene polyhydric alcohol, phosphate triethanolamine and antioxidant.
Japanese Published Application 9,049,167 describes the treatment of polyurethane elastic fiber with a neat-oiling agent comprising a mineral oil/polydimethylsiloxane lubricant and an alkanolamine organic phosphate to impart antistatic properties to the fiber between spinning and winding processes and to inhibit the adherence of scum onto the machine.
German Democratic Republic Published Application 296,515 describes a spin finish for synthetic filaments comprising alkylpoly-alkyleneglycol ether lubricants with 5-15% of a liquid dicarboxylic acid diester which may be applied as a neat oil.
U.S. Pat. No. 5,263,308 (Lee et al.) describes a method for ply-twisting nylon yarns (already spun) at high speeds by coating the nylon fibers with less than about 1% by weight of a finish containing an alkyl polyoxyethylene carboxylate ester lubricant composition of the general formula R.sub.1 --O--X.sub.n --(CH.sub.2).sub.m C(O)--O--R.sub.2, where R.sub.1 is an alkyl chain from 12 to 22 carbon atoms, X is --C.sub.2 H.sub.4 O-- or a mixture of --C.sub.2 H.sub.4 O-- and --C.sub.3 H.sub.6 O--, n is 3 to 7, m is 1 to 3, and R.sub.2 is an alkyl chain from 1 to 3 carbon atoms. The resulting ply-twisted yarn is especially suitable for use as pile in carpets. The finish may be applied neat, although it is preferably applied from an aqueous solution or emulsion, and may be used as a primary or secondary spin finish. The reference notes that these lubricants, which are described as oils, are advantageous over other lubricants in that they may be applied at very low levels and afford ease of wash-off during dying or scouring operations, both of which lead to improved soiling repellency (see, e.g., Col. 5, Lines 10-36).
While some of the above approaches may avoid the problems of sling-off and solids deposition associated with many low solids formulations, many of these approaches also involve the use of spin finish formulations that detrimentally affect the soiling characteristics, appearance, or hand of the finished article. Consequently, the use of these formulations requires scouring, with all of the disadvantages attendant thereto. Accordingly, there remains a need in the art for a spin finish formulation that does not cause sling-off or solids deposition, while also avoiding the need for scouring of the finished article.
One possible approach to improving the soiling characteristics of articles woven from fibers containing a spin finish is to add fluorochemicals to the spin finish composition. Such spin finish compositions are known, though these compositions are typically low solids formulations. The relatively high cost of fluorochemicals relative to hydrocarbon surfactants has made it impractical to use fluorochemicals in high solids or neat spin finishes, as it would be very difficult to uniformly treat a fiber with a very low add-on level of a high solids or neat fluorochemical. Furthermore, many conventional fluorochemicals are insoluble in high solids or neat spin finish formulations.
One example of a low solids fluorochemical spin finish composition is described in U.S. Pat. No. 4,566,981 (Howells). This reference describes the treatment of fibrous substrates with mixtures or blends of (a) a mixture of cationic and non-ionic fluorochemicals, (b) a fluorochemical poly(oxyalkylene), and/or (c) a hydrocarbon nonionic surfactant, which may be a poly(oxyalkylene). The reference also teaches that the hydrocarbon surfactant has a hydrophilic/lipophilic balance (HLB) in the range of about 13 to 16, and notes that surfactants with HLB values outside of this range do not promote emulsion stability and quality. The reference indicates that the mixtures or blends disclosed therein may be applied to substrates such as carpets from a spin finish emulsion (see, e.g., Examples 44-46) to impart desirable oil and water repellency and soil resistance to the substrate. However, all of the emulsions described are low solids compositions.
Other fluorochemical fiber treatments have utilized fluorochemicals as polymer melt additives in resins to modify the surface properties of fibers extruded or spun from the resins and/or to reduce the amount of spin finish required to lubricate the fiber. Thus, U.S. Pat. No. 5,025,052 (Crater et al.) describes water- and oil-repellent fibers comprising a fiber-forming synthetic or organic polymer and a fluorochemical oxazolidinone.
U.S. Pat. No. 5,244,951 (Gardiner) describes a durably hydrophilic fiber comprising thermoplastic polymer and fluoroaliphatic group-containing non-ionic compound dispersed within said fiber and present at the surface of the fiber.
U.S. Ser. No. 08/808,491 filed on Feb. 27, 1997, now U.S. Pat. No. 5,882,762 describes a plurality of filaments of a thermoplastic polymer containing a fluorochemical hydrophilicity-imparting compound, allowing for reduced levels of spin oil fiber lubricant on the fiber to impart satisfactory lubricity.
European Application 97.203812.9 describes fiber spun from filaments extruded from a mixture of a hydrophilic polymer and a hydrophilicity imparting compound, wherein the filaments have applied to them prior to spinning a spin finish comprising a fluorochemical oil and/or water repellent.
Yet another problem with conventional spin finish formulations has come to light with the emergence of polypropylene as a staple fiber in the carpet industry. Most spin finishes produced to date were developed for use on the older nylon and acrylic fibers, which have little tendency to adsorb hydrocarbon materials. In contrast to these fibers, the surface of polypropylene fibers is much more oleophilic. As a result, many conventional spin finishes are adsorbed into the polypropylene fiber surface to a much greater degree than is observed with nylon or acrylic fibers. This frequently causes degradation of the fiber, while also necessitating the use of excessive amounts of spin finish to attain desired lubricity properties.
One approach to the spin finish adsorption problem has been to add fluorochemicals to the polypropylene melt prior to the time at which the fiber is extruded, thereby rendering the fiber less oleophilic. This approach is described in some of the references noted above. However, the addition of fluorochemicals to the melt is not always desirable in that it often has an adverse effect on the hand or other characteristics of the resulting fiber.
Some spin finishes for polypropylene fibers are known outside of the carpet art, although many of these are not primary spin finishes. Thus, U.S. Pat. No. 5,246,988 (Wincklhofer et al.) describes the use of lubricants, which are the apparently liquid reaction products of 1 mole of either a C.sub.5 -C.sub.36 fatty acid or alcohol with 2 to 20 moles of ethylene oxide, as carriers for hindered amine anti-oxidants. These anti-oxidants/carriers are used to treat articles of high molecular weight thermoplastic films and fibers, thereby rendering the articles stable to heat and aging and allowing them to retain their breaking strength. Preferably, the lubricant comprises polyalkylene glycol (400) perlargonate, polyalkylene glycol (200) monolaurate and/or polyalkylene glycol (600) monoisostearate. However, the reference teaches that these finishes must be applied subsequent to solvent extraction of the polymer (see, e.g., Col. 4, Lines 6-10), and hence teaches the use of these materials as secondary finishes.
There is thus a need in the art for spin finish compositions which avoid the above noted infirmities associated with conventional spin finishes, and which can be used as a primary spin finish to provide good lubricity to polypropylene fibers without significant absorption into the fiber surface.
These and other needs are met by the present invention, as hereinafter described.